Sealed parking brake section for tamper resistant brake actuator

ABSTRACT

An improved tamper resistant brake actuator for sealing the pressurized parking brake section and inhibiting the unauthorized disassembly thereof. The spring housing has a first annular flange and the adapter base has a second annular flange that are cooperatively configured to define an annular channel when they are joined together. The periphery of the parking chamber diaphragm is provided with an expanded portion, preferably an integral o-ring, that sealably fits within the annular channel when the two annular flanges are engaged so as to provide radial sealing for the parking brake section. A ring-shaped annular retaining member or clamp is circumferentially disposed about the interface of the flanges and diaphragm periphery and is secured with a connecting mechanism that inhibits disassembly of the adapter base. The ends of the retaining member can be crimped, welded or bolted/riveted together. The retaining member is not required to axially clamp the diaphragm periphery.

CROSS-REFERENCE TO RELATED APPLICATIONS

None.

BACKGROUND OF THE INVENTION

A. Field of the Invention

The field of the present invention relates generally to vehicle braking systems that are operated by air or other fluids. More particularly, the present invention relates to spring brake systems having a brake actuator which utilizes a flexible diaphragm extending between two housing components to enclose a compressed spring and form a pressurized chamber within the joined housing unit. Even more particularly, the present invention relates to such brake systems that utilize the flexible diaphragm to seal the junction of the two housing components and a tamper resistant clamping mechanism to inhibit unauthorized disassembly of the housing unit.

B. Background

Most large commercial vehicles, such as heavy trucks and the like, utilize a hydraulic spring-operated braking system having a brake actuator that comprises a sealed pressure chamber for the compressed air or other hydraulic fluid used in the system and a powerful main compression spring disposed in a non-pressurized chamber as the actuator mechanism to provide the desired braking force. In normal driving or non-braking conditions, the pressure in the pressure chamber creates a force that exceeds the compression force provided by the main spring to prevent the brake actuator from actuating the brakes. This type of vehicle braking system is configured such that when the pressure in the pressure chamber is reduced below the level of force provided by the main spring, the main spring will drive a rod member, typically referred to as a push or actuator rod, through an aperture in the pressure chamber housing to operate the vehicle's brakes and stop the vehicle. One of the advantages of such a braking system is that if the vehicle's hydraulic system inadvertently loses its pressurized air, hydraulic oil or other fluid, the vehicle will be automatically placed in a braking condition instead of the situation where the brakes will not operate when the driver desires to slow or stop the vehicle. Naturally, for larger vehicles such as most commercial trucks and the like, the loss of hydraulic fluid leading to the inability to slow or stop the vehicle could lead to disastrous consequences for the driver, vehicle and other nearby drivers and their vehicles. The typical heavy truck and commercial vehicle also use this pressure released, brake on principle as the parking brake system for locking the vehicle's brakes in the braked condition when the vehicle is intended to remain still.

A common type of actuating mechanism utilized in heavy truck and commercial vehicle hydraulic spring brake systems comprises a multiple chamber actuator that is divided into a parking brake section having a non-pressurized spring chamber and a pressurized parking brake chamber, and a service brake section having a pressurizable upper service chamber and a non-pressurized lower service chamber. Typically, a one or two piece adapter base, which is also referred to as a flange case, is utilized to separate the actuator into the two sections. The upper side of the adapter base is used in conjunction with a spring housing, or head, to form the parking brake section and the lower side of the adapter base is used in conjunction with a service housing to form the service brake section. A flexible parking chamber diaphragm extending between flanges at the periphery of the adapter base and the spring housing divides the parking brake section into the non-pressurized spring chamber and the pressurized brake chamber. A flexible service chamber diaphragm extending between the adapter base and the service housing forms the pressurizable upper service chamber and the non-pressurized lower service chamber. The main compression spring is disposed in the non-pressurized spring chamber between an end wall of the spring housing and a moveable spring pressure plate that abuts the parking chamber diaphragm. A push rod and parking return spring are disposed in the pressurized parking brake chamber. The non-pressurized service chamber encloses an actuator rod plate, which is in abutting relationship with the service chamber diaphragm, at the end of an actuator rod and a service return spring disposed between the service housing and the actuator rod plate. A portion of the actuator rod extends outside of the service housing and is attached to a clevis or other guide member that couples to the vehicle's brake mechanism. The push rod slidably extends through a center seal in an aperture in the adapter base to push against the service chamber diaphragm and actuator rod plate.

In the normal non-braking driving condition, the pressure inside the pressurized parking brake chamber creates a force that exceeds the compression force of the main spring and, in the service brake section, the service return spring biases the actuator rod plate against the flexible service chamber diaphragm and the service chamber diaphragm toward the lower side of the adapter base. When the driver depresses the brake pedal, pressurized air or other fluid is directed into the upper service chamber, causing it to expand and force the service chamber diaphragm against the actuator rod plate to drive the actuator rod away from the brake actuator and cause the clevis to operatively engage the vehicle's braking system. When the driver stops the vehicle and sets the parking brake, air is released from the pressurized parking brake chamber, thereby allowing the force of the main compression spring to exceed the force created by the pressure in the parking brake chamber, causing the main spring to bias the spring pressure plate and the parking chamber diaphragm against the push rod disposed in the parking brake chamber. The push rod sealably moves through the center seal in the adapter base aperture to mechanically drive the service chamber diaphragm against the actuator rod plate, which in turn then drives the actuator rod away from the brake actuator to cause the clevis to operatively engage the vehicle's braking system. If the braking system inadvertently loses pressure, such as due to a leak in a pressure line or other loss of hydraulic pressure, then the brake actuator will automatically operate in the manner described above for setting the parking brake (i.e., the push rod will drive the service chamber diaphragm against the adapter rod plate to drive the actuator rod outwardly of the brake actuator).

For the heavy truck or commercial vehicle brake systems described above, as well as other similarly configured braking systems, two very important components for the effectiveness and safety of the braking system are the portion of the flexible parking chamber diaphragm that seals the junction of the spring housing and the adapter base and the tamper resistant mechanism that holds the spring housing and adapter base together in a manner that inhibits unauthorized disassembly of these components. As is well known in the art, the periphery portion of the flexible parking chamber diaphragm is sealably disposed between the joined annular flanges of the spring housing and the adapter base to provide the seal for the pressurized parking brake chamber so as to allow the pressure therein to overcome the force of the main spring. Failure to maintain the seal between the spring housing and the adapter base will result in engagement of the vehicle's brakes and inability to operate the vehicle. In addition, the mechanism that maintains the spring housing, adapter plate and parking chamber diaphragm in their cooperative relationship also ensures that the main spring remains safely contained within the brake actuator. As is well known in the art, the main spring is generally configured with a high spring constant that is compressed during the manufacturing process to store a substantial amount of potential energy, having been compressed from its normal, uncompressed height of nine to twelve inches to a compressed height of approximately three inches. Because the typical main spring exerts a 1,000 to 2,500 pound force on the spring housing, removal of the spring housing must be undertaken with a high amount of care to avoid severe injury or death to those near the brake actuator when it is taken apart. For this reason, as well as to prevent poor replacement seals, virtually all spring brake actuators in the United States and many other countries are configured such that the spring housing to adapter base junction is substantially tamper resistant and written warnings are provided on the brake actuator, typically stamped into the material used for the housing, to discourage any unauthorized entry therein.

Typically, the clamping mechanism utilized in prior art brake actuators to secure the spring housing and the adapter base together is also utilized to compress the parking chamber diaphragm between these two components so as to provide the sealing effect necessary to maintain the pressure in the pressurized parking chamber. The compression force provided by these types of clamping mechanisms is usually applied to the flanges on the spring housing and adapter base and to the parking chamber diaphragm in a generally axial direction, that being generally parallel to the center axis of the brake actuator (i.e., that which corresponds to the longitudinal axis of the push and actuator rods and the center of the flexible diaphragms). Examples of this type of configuration is well known in the art and are exemplified in a number of patents. For instance, U.S. Pat. No. 6,526,867 to Anderson discloses a brake actuator having a two-piece annular retaining member or clamp having a pair of inwardly protruding portions that engage the spring housing and adapter base flanges and an annular peripheral groove. A retaining ring disposed in the peripheral groove provides compressive force to hold the retaining member together and inhibit disassembly. The peripheral portion of the brake chamber diaphragm is axially compressed between the flanges of the spring housing and adapter base by the annular retaining member. U.S. Pat. No. 5,193,432 to Smith discloses a tamper resistant actuator having an annular retaining member configured with an axial lip on at least one of its inwardly protruding portions that engages an axial step on at least one of the spring housing or adapter base flanges to form the tamper resistant clamp. The peripheral portion of the brake chamber diaphragm is axially compressed between the flanges. U.S. Pat. No. 4,960,036 to Gummer, et al. discloses a tamper resistant brake actuator having an annular retaining member that joins the spring housing with the adapter base by having ends which are deformed beyond their elastic limit to clamp around the flanges of the spring housing and adapter base and axially compress the periphery of the brake housing diaphragm therebetween. U.S. Pat. No. 5,775,202 to Plantan, et al. discloses a clamping member for a brake actuator that is made from a roll of deformable material which is deformed around the flanges of the spring housing and adapter base to secure them together with the diaphragm compressed between the flanges. U.S. Pat. No. 6,131,501 to Smith, et al. discloses a spring brake adapter having a C-shaped annular retaining member disposed around the shoulder of the housing and an annular lip of the adapter base that is welded to either the housing or the adapter base to axially compress the parking chamber diaphragm between the housing and adapter base. A common aspect of the foregoing patents and related devices is that the annular retaining member axially compresses the periphery portion of the parking chamber diaphragm between the annular flanges of the spring housing and adapter base. As such the annular retaining member must be configured to provide enough clamping force to keep these two units together and to sufficiently compress the parking chamber diaphragm so as to seal the pressurized parking chamber.

Other tamper resistant brake actuators utilize specially modified or adapted spring housing and/or adapter base components that are configured to provide all or a portion of the clamping mechanism. For instance, U.S. Pat. No. 5,285,716 to Thompson discloses a tamper resistant brake actuator wherein a portion of the spring housing periphery that extends past a lip at the top of the adapter base is welded to the adapter base. The parking chamber diaphragm is axially clamped between a circumferential ledge of the housing and the adapter base lip. U.S. Pat. No. 6,536,329 to Anderson, et al. discloses a tamper resistant brake actuator wherein the outwardly extending flanges of the housing and adapter base are riveted or bolted together to axially clamp the periphery of the parking chamber diaphragm therebetween. U.S. Pat. No. 5,758,564 to Smith discloses a tamper resistant brake actuator wherein the periphery of the parking chamber diaphragm is axially compressed between an annular shoulder of the spring housing and a lip on the adapter base by the placement of a steel piece welded to an annular flange of the housing. U.S. Pat. No. 6,129,004, also to Smith, describes a similarly configured tamper resistant brake actuator. U.S. Pat. No. 6,405,636 to Anderson discloses a tamper resistant brake actuator wherein the housing has a flange configured with a collar portion having radially spaced apart tabs that engage the lower surface of an annular flange on the adapter base to axially compress the periphery of the parking chamber diaphragm therebetween. A retaining ring or wire is disposed around the spring housing to inhibit the tabs from deforming radially. Although these brake actuators are configured differently than the annular retaining member type set forth above (i.e., no ring-like retaining member or clamp), they still axially compress the periphery of the parking chamber diaphragm and, therefore, must be configured to both secure the housing and adapter base together and compress the diaphragm therebetween.

As an alternative to axial compression of the parking chamber diaphragm between the flanges or other components of the spring housing and adapter base, compressing the diaphragm in a generally or primarily radial direction reduces the amount of sealing force that is required to be supplied by the annular retaining member or other mechanism used to join the spring housing and adapter base together, thereby reducing the amount of stress the annular retaining member has to resist. An example of such a configuration is shown in U.S. Pat. No. 5,676,036 to Choinski, which discloses a tamper resistant brake actuator wherein the periphery of the spring housing is deformed into a securement groove in the adapter base to secure the components together. The periphery of the parking chamber diaphragm has a sealing bead received in a sealing groove formed in the adapter base and radially compressed therein by the side of the spring housing when the periphery thereof is deformed into the securement groove. U.S. Pat. No. 6,050,372 to Fisher discloses a tamper resistant brake actuator having the periphery of the parking chamber diaphragm clamped in an annular groove of the adapter base by the side wall of the spring housing. The spring housing and adapter base are secured together by the injection of molten metal into adjacent, but opposite facing, receptacles in the spring housing and adapter base. While these patents describe mechanisms that radially compress the periphery of the parking chamber diaphragm, they do not utilize ring-like annular retaining members or clamps that engage the flanges of the spring housing and adapter base, the manufacturing and use thereof which is common and familiar to those in the industry. Use of an annular retaining member or clamp eliminates the question of how tight to crimp the spring housing around the adapter base, as is done with U.S. Pat. No. 5,263,403. If the spring housing is crimped too tight it can crack the aluminum housing. If it is too loose, then it can leak. Unfortunately, once it is crimped it cannot be redone. Use of an annular retaining member or clamp generally provides a more fail-safe assembly during manufacture of the tamper resistant brake actuator.

What is needed, therefore, is an improved tamper resistant brake actuator that utilizes an annular retaining member to secure the spring housing and adapter base together, with the periphery of the parking chamber diaphragm disposed therebetween, which does not depend on axial compression force on the diaphragm as the primary sealing mechanism for the pressurized parking chamber. The desired brake actuator will utilize radial compression of the parking chamber diaphragm as the primary sealing force to prevent loss of pressure from within the pressurized parking chamber, thereby reducing the stress on the annular retaining member. Preferably, one or more mechanisms will be utilized to secure the annular retaining member around the flanges of the spring housing and adapter base so as to inhibit and discourage separation of the spring housing from the adapter base.

SUMMARY OF THE INVENTION

The sealed parking brake section for tamper resistant brake actuator of the present invention provides the benefits and solves the problems identified above. That is to say, the present invention discloses a spring housing and adapter base which provides a sealing arrangement that utilizes radial compression forces on the periphery of the parking chamber diaphragm to seal the pressurized parking chamber, thereby reducing the stress on the annular retaining member or clamp. As such the annular retaining member is primarily only required to resist the force of the main compression spring so as to hold the spring housing and adapter base together. In the preferred embodiments, the annular retaining member is secured around the flanges of the spring housing and the adapter base in a manner that substantially inhibits and discourages unauthorized separation of the spring housing and the adapter base.

In a preferred aspect of the present invention, the tamper resistant brake actuator comprises a spring housing having a first annular flange and an adapter base having a second annular flange that join together to form the parking brake section of the brake actuator. The first and second annular flanges are cooperatively configured such that when the spring housing is joined to the adapter base the first and second annular flanges define an annular channel circumferentially disposed about the brake actuator. In the preferred embodiment of the present invention, the first annular flange is configured with a generally radially outwardly extending shoulder and a generally downwardly extending collar and the second annular flange is configured with a generally upwardly extending collar and a generally radially outwardly extending shoulder that extends outward from the bottom or base of the collar. In this embodiment, the annular channel is defined by the shoulder and collar of the first flange and the collar and shoulder of the second flange when the spring housing is joined to the adapter base. A generally flexible diaphragm is disposed in the chamber defined by the spring housing and adapter base to divide the chamber into a non-pressurized spring chamber and a pressurized parking brake chamber. The preferred diaphragm has an expanded portion, preferably configured as an integral o-ring, at a periphery thereof that is sealably disposed, in a radially sealing manner, in the annular channel formed by the first and second flanges. The first annular flange, second annular flange and expanded portion define an interface circumferentially disposed about the brake actuator. A ring-shaped annular retaining member or clamp, made up of one or more clamp sections, is disposed about the interface so as to hold the spring housing and adapter base together and enclose the main spring in the spring chamber. In the preferred embodiment, the annular retaining member has a first inwardly protruding portion and a spaced apart second inwardly protruding portion defining a clamp channel therebetween that generally abuts the interface. In the preferred embodiment, the first inwardly protruding portion is in engagement with the shoulder of the first annular flange and the second inwardly protruding portion is in engagement with the shoulder of said second annular flange. To inhibit and generally prevent disassembly of the parking brake section (i.e., by separating the spring housing from the adapter base), the preferred embodiment includes a mechanism for securing a first end of the annular retaining member to a second end of the annular retaining member around the interface. The mechanism for securing the ends of the retaining member includes a crimped connection that crimps the outer connector of the first end to the inner connector of the second end, a welded connection that uses a weld to join the outer connector to the inner connector or a bolted/riveted connection that utilizes a bolt or rivet to join the outer connector to the inner connector.

In a preferred method of manufacturing the tamper resistant brake actuator of the present invention, utilizing the components described above and including the internal components of the parking brake chamber and spring chamber, the main spring and pressure plate are compressed in the spring housing and held in the compressed position with a T-bolt. The spring housing is then placed in an appropriate compression machine and then the adapter base, with the parking diaphragm placed thereon, is placed on top of the spring housing such that the parking diaphragm rests on the spring housing flange. The press then applies sufficient force to the adapter base to seat the expanded portion of the parking diaphragm in the annular channel formed between the adapter base and the spring housing in radially sealable engagement with the interior of the annular channel. Once the expanded portion is engaged within the annular channel, and while force is continued to be applied to the adapter base, the annular retaining member is disposed about the interface and the ends of the retaining member are connected together to secure the annular retaining member around the brake adapter. If a single piece annular retaining member is utilized, it is spread open, by bending the retaining member at a provided flexible section, a sufficient amount in order to place annular retaining member around the interface. The two or more ends of the retaining member are either crimped, welded or bolted/riveted together so as to form a substantially singular curvilinear annular retaining member around brake adapter and inhibit any unauthorized disassembly thereof.

Accordingly, it is a primary objective of the present invention to provide a sealed parking brake section for a tamper resistant brake actuator that provides the advantages discussed above and that overcomes the disadvantages and limitations associated with presently configured brake actuators.

It is also a primary objective of the present invention to provide a tamper resistant brake actuator that utilizes a cooperatively configured spring housing, adapter base and parking chamber diaphragm to provide a sealing mechanism wherein the primary seal is achieved through radial compressive force on the periphery of the diaphragm and utilizes an annular retaining member to hold the spring housing and adapter base together.

It is also an important objective of the present invention to provide a tamper resistant brake actuator having a spring housing which is secured to the adapter base in a manner that inhibits and discourages unauthorized separation thereof.

It is also an important objective of the present invention to provide a tamper resistant brake actuator that comprises a parking chamber diaphragm having an expanded portion, such as an integral o-ring, at the periphery thereof which is sealably disposed in an annular channel formed by the junction of the spring housing and adapter base in a manner that results in radial compressive forces being the primary seal for the pressurized brake chamber.

It is also an important objective of the present invention to provide a tamper resistant brake actuator that comprises a spring housing having a peripheral flange with a shoulder and collar portion configured to engage a cooperatively configured shoulder and collar portion of a peripheral flange of the adapter base so as to define an annular channel sized and configured to sealably engage the peripheral portion of the parking brake diaphragm disposed therein to seal the pressurized parking brake chamber.

It is also an important objective of the present invention to provide a method of securing a spring housing to an adapter base that provides a sealing mechanism which primarily seals in the radial direction to compress the parking chamber diaphragm in an annular channel defined by the opposing flanges of the spring housing and adapter base.

It is also an important objective of the present invention to provide a method of securing a spring housing to an adapter base that comprises the steps of forming a spring housing and an adapter base with cooperatively configured flanges, forming a parking chamber diaphragm with a expanded portion at the peripheral thereof, placing the peripheral portion of the diaphragm over the adapter base flange, compressing the main spring and pressure plate inside the spring housing and holding it in the compressed position with a T-bolt, placing the adapter base on the spring housing such that the parking diaphragm is inside the spring housing and the expanded portion is at the spring housing flange, applying pressure to the adapter base to force the spring housing flange over and around the peripheral portion of the diaphragm so as to form an annular channel with the expanded portion of the diaphragm disposed in the annular channel and then securing the spring housing to the adapter base with an annular retaining member in a manner that inhibits unauthorized separation thereof.

The above and other objectives of the present invention will be explained in greater detail by reference to the attached figures and the description of the preferred embodiment which follows. As set forth herein, the present invention resides in the novel features of form, construction, mode of operation and combination of components presently described and understood by the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings which illustrate the preferred embodiments and the best modes presently contemplated for carrying out the present invention:

FIG. 1 is a side perspective view of a double diaphragm spring brake actuator constructed in accordance with a preferred embodiment of the present invention showing use of a crimped annular retaining member to secure the spring housing to the adapter base;

FIG. 2 is a cross-sectional side view of the parking brake chamber showing the spring housing connected to the adapter base in accordance with the embodiment of the present invention having a welded annular retaining member;

FIG. 3 is a side view of the spring housing and adapter base of the brake actuator of FIG. 1;

FIG. 4 is a top view of the brake actuator of FIG. 1 showing the crimped two-piece annular retaining member configured according to a preferred embodiment of the present invention;

FIG. 5 is a top perspective view of one-half of the crimped two-piece annular retaining member of FIG. 4;

FIG. 6 is a top perspective view of both halves of the crimped two-piece annular retaining member of FIG. 4 shown in its non-engaged condition;

FIG. 7 is an isolated interior view of one of the crimped areas of the crimped two-piece annular retaining member of FIG. 6 shown in its non-engaged condition;

FIG. 8 is a top perspective view of the crimped two-piece annular retaining member of FIG. 6 shown in its engaged condition;

FIG. 9 is an isolated cross sectional view of the reduced thickness, flexible area of a one-piece annular retaining member configured according to one embodiment of the present invention;

FIG. 10 is a top perspective view of a welded one-piece annular retaining member configured according to one embodiment of the present invention;

FIG. 11 is a top view of a brake actuator having the welded one-piece annular retaining member of FIG. 10;

FIG. 12 is a side view of a double diaphragm spring brake actuator constructed in accordance with the embodiment of the present invention showing use of a welded annular retaining member to secure the spring housing to the adapter base;

FIG. 13 is a top view of the brake actuator of FIG. 12 showing the welded two-piece annular retaining member configured according to a preferred embodiment of the present invention;

FIG. 14 is a top perspective view of one-half of the welded two-piece annular retaining member of FIG. 13;

FIG. 15 is a top perspective view of the welded two-piece annular retaining member of FIG. 13 shown in its non-welded condition;

FIG. 16 is a top perspective view of a brake actuator constructed in accordance with the embodiment of the present invention showing use of a bolted one-piece annular retaining member to secure the spring housing to the adapter base; and

FIG. 17 is a top perspective view of the bolted one-piece annular retaining member of FIG. 16 shown in its non-bolted condition.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the figures where like elements have been given like numerical designations to facilitate the reader's understanding of the present invention, and particularly with reference to the embodiments of the tamper resistant brake actuator of the present invention illustrated in the figures, various preferred embodiments of the present invention are set forth below. The enclosed description and drawings are merely illustrative of preferred embodiments and represent several different ways of configuring the present invention. Although specific components, materials, configurations and uses of the present invention are illustrated and set forth in this disclosure, it should be understood that a number of variations to the components and to the configuration of those components described herein and in the accompanying figures can be made without changing the scope and function of the invention set forth herein. For purposes of this disclosure, references are generally to use of the present invention with a double diaphragm spring brake actuator, however, it is understood that the disclosure herein applies to other types of brake actuators having a two-piece housing to sealably enclose a pressure member therein.

A preferred embodiment of a spring brake actuator that is manufactured out of the components and configured pursuant to the concepts and principles of the present invention is shown generally as 10 in the figures. As shown generally in FIGS. 1, 2 and 12, spring brake actuator 10 is particularly configured for use with the annular retaining member 12 of the present invention, as is set forth in more detail below and in the accompanying figures. The embodiment of the spring brake actuator 10 shown in FIG. 1 generally comprises a parking brake section 14 and service brake section 16. As shown, adapter base 18 separates parking brake section 14 and service brake section 16, forming the lower wall of parking brake section 14 and the upper wall of service brake section 16. In some spring brake adapters 10, adapter base 18 is formed from one or more adapter plates. Generally, adapter base 18 is made out of aluminum or other metals. Spring housing 20 is the upper wall of parking brake section 14 and service housing 22 is the lower wall of service brake section 16. An elastic parking chamber diaphragm 24 divides parking brake section 14 into a non-pressurized spring chamber 28 and a pressurized parking brake chamber 30. Although not shown in the figures, an elastic service chamber diaphragm extends across the lower end of adapter base 18 at service brake clamp 32 to divide service brake section 16 into a pressurizable upper service chamber and a non-pressurized lower service chamber. The main compression spring 34 is disposed in spring chamber 28 generally between spring housing 20 and a moveable spring pressure plate 36. Spring pressure plate 36 is configured to move downward against parking chamber diaphragm 24 and upper push rod plate 38, which is attached to push rod 40. The movement of main spring 34 against parking chamber diaphragm 24 and upper push rod plate 38 drives push rod 40 downward through a bushing or center seal assembly 42, which is in sealable relation to push rod 40 to allow push rod 40 to move therethrough without loss of pressure from the pressurized parking brake chamber 30. Parking return spring 44, disposed in parking brake chamber 30 around push rod 40, returns upper push rod plate 38 to its non-braking position, as is generally shown in FIG. 2.

At the opposite end of push rod 40 from upper push rod plate 38 is a lower push rod plate (not shown) that is configured to push downward against service chamber diaphragm and actuator rod plate (not shown) to drive actuator rod 46 in a generally downward direction. A clevis or other operating mechanism at the opposite end of actuator rod 46 is configured to operatively couple to the vehicle's braking system (not shown) to brake the vehicle when actuator rod 46 is driven downward by the action of the service chamber diaphragm which, as described below, occurs either as a result of downward motion by push rod 40 or the pressurization of the upper service chamber. A service return spring (not shown) is configured to return actuator rod 46 to the non-braking condition shown in FIG. 2. Typically, brake actuator 10 is mounted in place on the vehicle and a hydraulic system (not shown) hydraulically connects to parking brake chamber 30 and to the upper service chamber to add or remove pressurized fluid (i.e., air) from parking brake chamber 30 or the upper service chamber to set or unset, as the case may be, the vehicle's parking brake or driving brakes.

In operation during normal driving or non-braking condition, shown generally in FIG. 2, the pressure inside parking brake chamber 30 creates a force that exceeds the compression force of main spring 34, the parking return spring biases the upper push rod plate upward against parking chamber diaphragm 24 and the service return spring biases the actuator rod plate against the service chamber diaphragm toward the lower end of adapter base 18. When the driver presses the brake pedal (not shown) to reduce the vehicle's speed or stop the vehicle, pressurized air or other fluid is directed into the upper service chamber, thereby causing it to expand and force the service chamber diaphragm downward against the actuator rod plate to drive actuator rod 46 away from brake actuator 10 to cause the clevis to operatively engage the vehicle's braking system. When the driver stops the vehicle and sets the parking brake to keep the vehicle in a stopped condition, air or other hydraulic fluid is released from the pressurized parking brake chamber 30 such that the force of main compression spring 34 exceeds the pressure force in parking brake chamber 30, thereby causing main spring 34 to bias spring pressure plate 36 and parking chamber diaphragm 24 against upper push rod plate 38 disposed in parking brake chamber 30 to drive push rod 40 in a generally downward direction. Push rod 40 sealably moves through the center seal bushing assembly 42 disposed in adapter base 18 to mechanically drive the service chamber diaphragm against the actuator rod plate, which in turn drives actuator rod 46 away from brake actuator 10 to cause the clevis to engage the vehicle's braking system. If the vehicle's braking system inadvertently loses pressure, for instance due to a leak in a pressure line or some other loss of hydraulic pressure, then brake actuator 10 will automatically operate in the manner described above for setting the vehicle's parking brake (i.e., main spring 34 will drive push rod 40 against the service chamber diaphragm to drive actuator rod 46 outwardly of the brake actuator 10).

As discussed above, one of the primary operational concerns is that the interface, shown as 48 in FIG. 2, of the adapter base 18, spring housing 20 and parking chamber diaphragm 24 is configured to seal pressurized parking brake chamber 30 in order to overcome the force of main spring 34 during normal driving conditions. Failure to provide an adequate seal at interface 48 will result in the loss of pressure from parking brake chamber 30 and, therefore, the downward motion of actuator rod 46 that operates the vehicle's braking system. As also discussed above, one of the primary safety concerns is that unauthorized removal of spring housing 20 from adapter base 18 be adequately inhibited that most persons will be discouraged from attempting to remove spring housing 20 without use of the proper equipment and safety procedures. Removal of spring housing 20 by persons without the proper equipment and/or proper training can result in severe injury or even death to persons standing near brake actuator 10 when the force of main spring 34 is released. Heretofore, prior art brake actuators have primarily relied on axial compression of the parking chamber diaphragm 24 between adapter base 18 and spring housing 20 at interface 48 to obtain the desired seal and the use of a ring-like clamp for the annular retaining member to hold adapter base 18 and spring housing 20 together at interface 48 to provide a generally tamper resistant brake actuator. The tamper resistant brake actuator 10 of the present invention utilizes a sealing configuration that results in the primary seal for parking brake chamber 30 being the radial compression of parking chamber diaphragm 24 at interface 48 with the ring-like clamp annular retaining member 12 holding adapter base 18 and spring housing 20 together.

Like the typical prior art brake actuator, spring housing 20 of brake actuator 10 of the present invention has a side wall 50, which is generally cylindrical or frustoconical in shape, with a first annular flange 52 at the periphery thereof, the spring housing side of adapter base 18 has a side wall 54, which is also generally cylindrically or frustoconically shaped, with a second annular flange 56 and parking chamber diaphragm 24 has a periphery 58 in sealed engagement with annular flange 52 of spring housing 20 and annular flange 56 of adapter base 18. As described in more detail below, annular retaining member 12 engages annular flange 52 of spring housing 20 and annular flange 56 of adapter base 18 to secure spring housing 20 to adapter base 18. Unlike the prior art brake actuators, however, the interface 48 of adapter base 18, spring housing 20 and parking chamber diaphragm 24 are uniquely configured so as to obtain the desired radial compression of the periphery 58 of parking chamber diaphragm 24 and the desired seal for parking brake chamber 30. As best shown in FIGS. 2 and 9, in the preferred embodiment of the present invention flange 52 of spring housing 20 has a generally radially outwardly extending shoulder 60, extending outwardly from side wall 50, and a generally downwardly extending collar 62 at the outward end of shoulder 60. Also in the preferred embodiment, flange 56 of adapter base 18 has a generally upwardly extending collar 64 and a generally radially outwardly extending shoulder 66 extending outwardly from the base of collar 64. For assembly purposes, it is preferred that the ends of collar 62 and shoulder 66 are cooperatively beveled so as to facilitate the placement of collar 62 in engagement with shoulder 66. When spring housing 20 is joined to adapter base 18 at interface 48, as explained in more detail below, shoulder 60 and collar 62 of spring housing flange 52 and collar 64 and shoulder 66 of adapter base flange 56 define an annular channel 68 therebetween. In one embodiment, annular channel 68 has a generally rectangular or square cross-section.

As shown in FIGS. 2 and 9, in the preferred embodiment of the present invention periphery 58 of parking chamber diaphragm 24 has an expanded portion 70, disposed in annular channel 68, that is sized and configured to sealably engage the interior surfaces of annular channel 68 so as to seal, in the radial direction, parking brake chamber 30. Preferably, expanded portion 70 is in the nature of an annularly disposed, integral O-ring or the like that has a cross-sectional diameter or width dimension that is greater than the width of annular channel 68. In a preferred embodiment, the outside diameter of parking chamber diaphragm 24 at expanded portion 70 is approximately equal to the outer diameter of annular flange 56 of adapter base 18 (i.e., at the outer edge of shoulder 66) and the inside diameter of parking chamber diaphragm at expanded portion 70 is approximately equal to the diameter of annular flange 56 of adapter base 18 at the outer surface of collar 64. Also in the preferred embodiment, the inner diameter of flange 52 of spring housing 20 measured at the inside wall of collar 62 is approximately equal to or minimally greater than the diameter of annular flange 56 of adapter base 18 measured at the outer edge of shoulder 66. In this configuration, in the absence of any applied force, collar 62 of spring housing 20 will rest on the outer edge of expanded portion 70 of parking chamber diaphragm 24. When force is applied to the top of spring housing 20, during the assembly of brake actuator 10, the collar 62 of spring housing 20 will be forced over the expanded portion 70 of parking chamber diaphragm 24 until collar 62 will be at or near abutting relationship with shoulder 66 of adapter base annular flange 56, as shown in FIGS. 2 and 9. The force applied to spring housing 20 will radially compress expanded portion 70 of parking chamber diaphragm 24 against collar 64 of adapter base annular flange 56, compressing shaded compression area 72 in FIG. 9, to provide the seal necessary for parking brake chamber 30. The radial compression of expanded portion 70 provides the primary sealing interface for parking brake chamber 30. Also in this preferred configuration, a lesser amount of sealing interference, shown as shaded compression areas 74 in FIG. 9, will take place between the inward end of shoulder 60 and the upward end of collar 64. In addition to providing a secondary sealing interface, the compression areas 74 will provide a slight tension on annular retaining member 12 so the spring housing 20 will not wiggle or move in relation to adapter base 18. Configured as described above, the improved brake actuator 10 of the present invention satisfies the operational concern with regard to the sealing of parking brake chamber 30 and reduces the stress on annular retaining member 12 by utilizing radial compression of parking chamber diaphragm 24 at expanded portion 70 thereof.

With regard to a generally tamper resistant mechanism to inhibit or at least discourage the unauthorized disassembly of brake actuator 10, the preferred embodiment of the present invention utilizes a generally curvilinear ring-shaped annular retaining member 12 to cooperatively engage first annular flange 52 and second annular flange 56 so as to hold spring housing 20 and adapter base 18 together with sufficient force to counteract the compression force of main spring 34. As explained in more detail below, annular retaining member 12 is joined at one or more ends thereof by either crimping (FIGS. 1 and 4 through 8), welding (FIGS. 2 and 10 through 15) or bolting/riveting (FIGS. 16 and 17). As also explained below, annular retaining member 12 can comprise two or more separate curvilinear clamp sections, such as first clamp section 76 and second clamp section 78 best shown in FIGS. 4, 6, 8, 13 and 15, that are joined at the ends or a generally continuous curvilinear single piece clamp 80 that has a flexible portion 82 joining first integral section 80 a and second integral section 80 b, as best shown in FIGS. 9 through 11, 16 and 17, for assembly of brake actuator 10. The preferred embodiments are those utilizing the two or more clamp sections due to the fact that, as explained in more detail below, flexible portion 82 requires a portion of annular retaining member 12 to have a thinner wall in order to get the flexibility necessary to place annular retaining member 12 around interface 48 during the assembly process. As those skilled in the art will recognize, such a reduced wall thickness results in annular retaining member 12 being more vulnerable to being cut by a person desiring to gain unauthorized access to the interior of brake actuator 12. As configured for the present invention, the use of two or more clamp sections 76 and 78 provides a more tamper resistant brake actuator 10 because a person wanting to take apart brake actuator 10 having such a configuration will have to cut through annular retaining member 12, first annular flange 52 and second annular flange 56, a much more difficult task.

Except for the manner in which the ends of the various sections are joined, annular retaining member 12 is configured the same for each of the aforementioned embodiments. Annular retaining member 12 is a substantially continuous curvilinear ring-shaped member having a generally C-shaped cross-section with a body portion 84 having a first inwardly protruding portion 86 and a second inwardly protruding portion 88 in spaced apart relation to define a clamp channel 90 therebetween and substantially coextensive therewith, as best shown in FIGS. 5, 6, 10, 14, 15 and 17. Each separate piece of annular retaining member 12, whether the two-piece or one-piece configuration, has a first end 92 and second end 94 that are cooperatively configured so as to engagedly interconnect, by the mechanisms described below, so as to completely encircle interface 48. When first end 92 and second end 94 are joined together in the manner described below, annular retaining member 12 will hold spring housing 20 and adapter base 18 together in a manner that inhibits the unauthorized separation thereof. The inner diameters of first 86 and second 88 inwardly protruding portions is less than the outer diameters of first 52 and second 56 annular flanges, respectively, so that inwardly protruding portions 86 and 88 will engage annular flanges 52 and 56 to hold spring housing 20 and adapter base 18 in cooperative engagement with the periphery 58 of parking chamber diaphragm 24 disposed therebetween, as set forth above. As shown in FIGS. 2 and 9, when clamp channel 90 is disposed around interface 48, body portion 84 will be in a generally abutting relationship with the side of collar 62 of first flange 52 and with the end of shoulder 66 of second flange 56. Because the compressive force against periphery 58 of parking chamber diaphragm 24 is provided in a radial direction due to the interaction of expanded portion 70 in annular channel 68, as described above, first 86 and second 88 inwardly protruding portions of annular retaining member 12 only need to resist the force of main spring 34. In prior art configurations, first 86 and second 88 inwardly protruding portions of annular retaining member 12 are also required to provide the axial force necessary to axially compress the periphery 58 of parking chamber diaphragm 24 to seal parking brake chamber 30. The configuration of the present invention reduces the stress loading on inwardly protruding portions 86 and 88, as well as on the remaining components of annular retaining member 12.

The preferred embodiment of brake actuator 10 of the present invention utilizes the two-piece crimped clamp for annular retaining member 12, which is best shown in FIGS. 4 through 6 and 8. Crimp connection 96 is made up of an outer connector 98 at first end 92 and an inner connector 100 at second end 94. During assembly, with first clamp section 76 and second clamp section 78 placed around brake actuator 10 at interface 48, outer connector 98 is placed over inner connector 100, as shown in FIGS. 6 and 7, so the two connectors may be engaged to fix annular retaining member 12 on brake actuator 10. In the preferred embodiment, outer 98 and inner 100 connectors are engaged by the use of cooperatively configured tabs that are crimped into place to join the first 92 and second 94 ends together so as to maintain spring housing 20 attached to adapter base 18. Preferably, outer connector 98 has a center section 102 with one or more inwardly bendable tabs 104 that are configured to be bent by a crimping machine or like device over center section 106 of inner connector 100, as shown in the pre-crimped condition in FIGS. 6 and 7. When crimped, tabs 104 will abuftingly engage the top of center section 106, as shown in FIG. 8. When bendable tabs 104 are crimped over center section 106, retaining tabs 108 on inner connector 100 at second end 94 will keep crimped connector 96 from pulling apart by cooperatively engaging the sides of bendable tabs 104 when they are crimped. Support tabs 110 on outer connector 98 and support tabs 112 on inner connector 100 are configured to be placed in supporting engagement, as best shown in FIG. 7, when inner connector 100 is disposed inside outer connector 98. During assembly, outer connector 98 of first clamp section 76 is placed over inner connector 100 of second clamp section 78 until supporting tabs 110 and 112 are properly aligned and then a crimping device or machine is utilized to crimp bendable tabs 104 of outer connector 98 over center section 106 of inner connector 100 until tabs 104 are sufficiently engaged therewith and with retaining tabs 108. This same process is repeated to connect outer connector 100 of second clamp section 78 with inner connector 98 of first clamp section 76 to fully encircle brake actuator 10 at interface 48. Once crimped, crimped connector 96 will provide sufficient force to retain first clamp 52 in cooperative engagement with second clamp 56, as discussed above, so as to overcome the force of main spring 34 and maintain spring housing 20 on adapter base 18. Because annular retaining member 12 is in abutting relationship with first 52 and second 56 annular flanges and is effectively provided with a double thick clamp at crimped connector 96, any unauthorized disassembly of brake actuator 10 will be substantially inhibited. With regard to use of crimp connector 96, those skilled in the art will recognize that it is important to choose materials and configurations which can be suitably crimped over and engage the opposite end of annular retaining member 12. For instance, it is important that there is sufficient space to crimp the connector and that the crimping jaws are able to plastically deform the material used for annular retaining member 12 so that it will remain in the crimped condition.

In another embodiment of brake actuator 10 of the present invention utilizes a one-piece clamp for annular retaining member 12, which is best shown in FIGS. 9 through 11 (with FIGS. 10 and 11 showing a welded connection, which is explained in more detail below). As best shown in FIG. 10, the welded connection, first end 92 of single clamp 80, positioned at the end of first integral section 80 a, comprises outer connector 98 and second end 94 at the end of first integral section 80 b comprises inner connector 100. For a crimped single piece annular retaining member 12 (not shown), tabs 104 of outer connector 98 are crimped over center section 106 of inner connector 100 to cooperatively engage crimped connector 96. Elsewhere on single clamp 80, although not required it will generally be opposite crimped connector 96, is located flexible section 82 to allow sufficient bending of single clamp 80 to facilitate the assembly thereof around interface 48 of brake actuator 10. As those skilled in the art will readily recognize, single clamp 80 must be configured to sufficiently bend so as to allow single clamp 80 to be positioned around first 52 and second 54 clamps (which is not a problem for the two or more separate clamp sections, such as first 76 and second 78 clamp sections) and provide generally even compression during assembly. In a preferred embodiment, the necessary flexibility for flexible section 82 is achieved by eliminating first 86 and second 88 inwardly protruding sections at flexible section 82, leaving only body portion 84. If necessary, the thickness of body portion 84 can be reduced at flexible section 82 to provide further flexibility. During assembly, single clamp 80 is spread apart by grasping first 80 a and second 80 b integral sections and bending single clamp 80 at flexible section 82 a sufficient amount to allow single clamp 80 to be placed around and over first 52 and second 56 annular clamps. Once positioned around interface 48, single clamp 80 is bent inward at flexible section 82 to join first end 92 and second end 94 thereof with outer connector 98 placed outside inner connector 100 so that it may be crimped as discussed above or welded or bolted as discussed below. Once crimped, annular retaining member 12 will provide sufficient force to overcome main spring 34 and maintain spring housing 20 on adapter base 18. As discussed above, however, single clamp 80 may be more vulnerable to unauthorized disassembly by those persons who are willing to risk the dangers associated therewith. The configuration of reduced section 82 described above will be easier to cut through due to the fact that first 86 and second 88 inwardly protruding portions are not utilized at reduced section 82. The risks associated with such activity may have to be weighed against the reduced assembly costs associated with use of single clamp 80 versus the two-pieces of first 76 and second 78 clamp sections discussed above.

In an alternative configuration of brake actuator 10 of the present invention, annular retaining member 12 uses a welded connection 114 to connect the first 92 and second 94 ends of the clamp sections, such as the first 76 and second 78 clamp sections of the two-piece configuration shown in FIGS. 13 through 15 or the first 80 a and second 80 b integral sections of the one-piece clamp 80 shown in FIGS. 10 and 11. Other than the use of a welded connection 114, which results in a different configuration for outer connector 98 and inner connector 100, the basic configuration of annular retaining member 12 for a single clamp configuration is the same as that described above. The one-piece clamp 80 has first 80 a and second 80 b integral sections joined by flexible section 82 and the two-piece clamp has first clamp section 76 and second clamp section 78. As set forth above, in either configuration outer connector 98 is positioned over inner connector 100 to secure annular retaining member 12 around brake actuator 10 at interface 48. In the preferred embodiment of welded connection 114, outer connector 98 has one or more apertures 116 (one shown in the figures) and inner connector 100 has a weld receiving area 118, which can be a tab or tab-like extension member 120 best shown in FIG. 14 or merely the outer side of body portion 84. As will be understood by those skilled in the art, in the preferred embodiment outer connector 98 and inner connector 100 are cooperatively configured such that outer connector 98 can substantially cover inner connector 100. A weld, shown as 122 in FIG. 12, fills aperture 116 against tab extension 120 so as to fixedly join outer connector 98 and inner connector 100. Weld 122 can be applied by mig welding or any other technique which is suitable and cost efficient for brake adapter 10. The welding process and material used for weld 122 will be beneficially selected based on the materials utilized for annular retaining member 12. In general, although welded connection 114 of this embodiment is believed to be a less technically difficult manner to obtain the desired connection (therefore perhaps easier and faster to get into production), it is nevertheless believed to be less preferred than crimped connection 96 due to the extra materials required for weld 122 and because touch-up of weld 122 (i.e., sanding to a smooth finish) is generally required. As set forth above, the two or more piece configuration of FIGS. 13 through 15 is preferred over the one-piece configuration of FIGS. 10 and 11 due to the increased tamper resistant nature of the two-piece connection versus the use of flexible section 82 for the one-piece connection.

In another alternative configuration of brake actuator 10 of the present invention, annular retaining member 12 uses a bolted or riveted connection 124 to connect the first 92 and second 94 ends of the clamp sections, such as the first 80 a and second 80 b integral sections of the one-piece clamp 80 shown in FIGS. 16 and 17 or the first 76 and second 78 clamp sections of the two-piece configuration (not shown). Other than the use of a bolted or riveted connection 124, which results in a different configuration for outer connector 98 and inner connector 100, the basic configuration of annular retaining member 12 for this configuration is the same as that described above for crimped connection 96. The one-piece clamp 80 has first 80 a and second 80 b integral sections joined by flexible section 82 and, although not shown, the two-piece clamp has first clamp section 76 and second clamp section 78. As set forth above, in either configuration outer connector 98 is positioned over inner connector 100 to secure annular retaining member 12 around brake actuator 10 at interface 48. In the preferred embodiment of bolted or riveted connection 124, outer connector 98 has an aperture 126, shown in FIG. 17, and inner connector comprises a tab extension 128 having a corresponding aperture (not shown) to aperture 126 when outer connector 98 is joined to inner connector 100, as shown in FIG. 16. Aperture 126 and the corresponding aperture in tab extension 128 are sized and configured to receive connecting element, such as tamper resistant bolt 130 or a rivet (not shown) therethrough. In the bolted configuration of this embodiment, positioned behind or inward of tab extension 128 is a nut 132 or other receiving member for connecting element 130. In one embodiment, nut 132 is loose behind tab extension 128. In the preferred embodiment, however, nut 132 is affixed to the back side of tab extension 128 to ease the assembly of annular retaining member 12 around interface 48. To inhibit or discourage disassembly of spring housing 20 from adapter base 18, it is preferred that the head of the connecting element 130, whether a bolt or rivet, be ground off so that it cannot be easily removed. In general, bolted/riveted connection 124 of this embodiment is believed to be less preferred than crimped connection 96 due to the extra materials required for connecting element 130 and, if needed, nut 132 and due to the grinding of the head of connecting element 130 (i.e., sanding to a smooth finish) as is generally required to inhibit disassembly. In addition, the use of nut 132 makes it relatively easier for a person to cut through bolted/riveted connection 124 than the crimped connection 96 or welded connection 114 described above. Unlike these other configurations, it is likely that the one-piece configuration shown in FIGS. 16 and 17 is preferred due to the less materials and follow-up work required without the benefit of the multiple piece configurations discussed above (i.e., the connector being harder to cut through).

Assembly of brake adapter 10 of the present invention is accomplished by first providing a spring housing 20 having a first annular flange 52 configured with an outwardly extending shoulder 60 and a downwardly extending collar 62, an adapter base 18 having a second annular flange 56 configured with an upwardly extending collar 64 and an outwardly extending shoulder 66 that extends outward from the base of collar 64 such that first 52 and second 56 annular flanges form an annular channel 68, and a parking chamber diaphragm 24 having a periphery 58 configured with an expanded portion 70, preferably in the nature of an integral o-ring, that is configured to sealably fit within annular channel 68. Main spring 34 and pressure plate 36 are compressed in spring chamber 28 and held in the compressed position with a T-bolt. With the components of parking brake chamber 30 in place, the periphery 58 of parking chamber diaphragm 24 is placed snugly over the collar 64 of second annular flange 56 until the bottom of expanded portion 70 abuts shoulder 66. Spring housing 20 is then placed in an appropriate compression machine and adapter base 18, with parking diaphragm 24 placed thereon, is placed on top of spring housing 20 such that periphery 58 of parking diaphragm 24 rests on spring housing flange 62. The press then applies sufficient force to adapter base 18 to seat expanded portion 70 of parking diaphragm 24 in annular channel 68 formed between adapter base 18 and spring housing 20 in radially sealable engagement with the interior of annular channel 68. Once expanded portion 70 is engaged within annular channel 68, and while force is continued to be applied to adapter base 18, annular retaining member 12 is disposed about interface 48 and the ends of annular retaining member 12 are connected together to secure annular retaining member 12 around brake adapter 10. Once expanded portion 70 is engaged within annular channel 68, annular retaining member 12 is disposed about interface 48 and the first 92 and second 94 ends thereof are connected together as described above. If a single clamp 80 configuration is utilized, annular retaining member 12 is spread open a sufficient amount to allow annular retaining member 12 to be placed around interface 48. Depending on whether crimped connection 96, welded connection 114 or bolt/rivet connection 124 is utilized the connection is either crimped, welded or bolted/riveted to form a substantially singular curvilinear annular retaining member 12 around brake adapter 10.

The present invention, therefore, provides an improved tamper resistant brake actuator 10 having an improved sealed parking brake section 14 which is relatively easy and inexpensive to produce and assemble. The radial compression of the periphery 58 of the parking chamber diaphragm 24 reduces the stress on annular restraining member 12, which with the present invention only needs to overcome the force of main spring 34. The brake actuator 10 of the present invention utilizes conventional and readily available materials and components, all of which are well known to those skilled in the art.

While there are shown and described herein certain specific alternative forms of the invention, it will be readily apparent to those skilled in the art that the invention is not so limited, but is susceptible to various modifications and rearrangements in design and materials without departing from the spirit and scope of the invention. In particular, it should be noted that the present invention is subject to modification with regard to the dimensional relationships set forth herein and modifications in assembly, materials, size, shape, and use. For instance, as will be readily appreciated by those skilled in the art, the present invention is adaptable to a variety of different types of brake actuators that have a housing portion that encloses a power spring and flexible diaphragm between the housing and a adapter base, flange or the like. While the present invention is described in connection with a diaphragm brake actuator, it is likely that the invention may be useful with other fluid brake actuators, such as a piston spring actuator. 

1. A tamper resistant brake actuator, comprising: a spring housing having a first annular flange; an adapter base having a second annular flange, said spring housing and said adapter base joined at said first annular flange and said second annular flange; an annular channel defined by said first annular flange and said second annular flange; a generally flexible diaphragm having an expanded portion at a periphery thereof, said expanded portion sealably disposed in said annular channel, said first annular flange, said second annular flange and said expanded portion defining an interface, said expanded portion sealingly engaging said annular channel in a generally radial direction; and an annular retaining member secured about said interface, said annular retaining member having a pair of spaced apart inwardly protruding portions, one of said inwardly protruding portions in engagement with said first annular flange and the other of said inwardly protruding portions in engagement with said second annular flange, said annular retaining member configured so as to inhibit separation of said spring housing and said adapter base.
 2. The brake actuator of claim 1, wherein said first annular flange has a generally radially outwardly extending shoulder and a generally downwardly extending collar and said second annular flange has a generally upwardly extending collar and a generally radially outwardly extending shoulder extending outward from the base of said collar.
 3. The brake actuator of claim 2, wherein said annular channel is defined by said shoulder and said collar of said first annular flange and said collar and said shoulder of said second annular flange.
 4. The brake actuator of claim 2, wherein said pair of inwardly protruding portions comprises a first inwardly protruding portion and a spaced apart second inwardly protruding portion defining a clamp channel therebetween, said first inwardly protruding portion in engagement with said shoulder of said first annular flange and said second inwardly protruding portion in engagement with said shoulder of said second annular flange, said clamp channel generally abutting said interface.
 5. The brake actuator of claim 1, wherein expanded portion comprises an integral o-ring.
 6. The brake actuator of claim 1, wherein said pair of inwardly protruding portions comprises a first inwardly protruding portion and a spaced apart second inwardly protruding portion defining a clamp channel therebetween, said first inwardly protruding portion in engagement with said first annular flange and said second inwardly protruding portion in engagement with said second annular flange, said clamp channel generally abutting said interface.
 7. The brake actuator of claim 1 further comprising means for securing a first end of said annular retaining member to a second end of said annular retaining member so as to further inhibit separation of said spring housing and said adapter base.
 8. The brake actuator of claim 7, wherein said securing means comprises an outer connector at said first end of said annular retaining member and an inner connector at said second end of said annular retaining member, said outer connector having one or more bendable tabs configured to engage a center section of said inner connector.
 9. The brake actuator of claim 8, wherein said securing means further comprises one or more retaining tabs on said inner connector, said retaining tabs configured to prevent separation of said first end and said second end of said annular retaining member.
 10. The brake actuator of claim 7, wherein said securing means comprises an outer connector at said first end of said annular retaining member and an inner connector at said second end of said annular retaining member, said outer connector having one or more apertures.
 11. The brake actuator of claim 10, wherein at least one of said one or more apertures overlays a weld receiving area on said inner connector, said outer connector and said inner connector interconnected by a weld.
 12. The brake actuator of claim 11, wherein said inner connector comprises a tab extension member at said second end of said annular retaining member, said weld receiving area on said tab extension.
 13. The brake actuator of claim 10, wherein at least one of said one or more apertures of said outer connector overlays an aperture in said inner connector, said apertures of said outer connector and said aperture of said inner connector sized and configured to receive a connecting element therein, said connecting element configured to securedly connect said first end and said second end of said annular retaining member.
 14. The brake actuator of claim 13, wherein said securing means further comprises a nut at said inner connector.
 15. The brake actuator of claim 1, wherein said annular retaining member comprises a two or more clamp sections disposed about said interface to form a generally continuous curvilinear member, each of said clamp sections having a first end securedly joined to a second end of an adjacent clamp section.
 16. A tamper resistant brake actuator, comprising: a spring housing having a first annular flange, said first annular flange comprising a generally radially outwardly extending shoulder and a generally downwardly extending collar; an adapter base having a second annular flange, said second annular flange comprising a generally upwardly extending collar and a generally radially outwardly extending shoulder, said shoulder extending outward from the base of said collar, said spring housing and said adapter base joined at said first annular flange and said second annular flange; an annular channel defined by said shoulder and said collar of said first annular flange and said collar and said shoulder of said second annular flange; a generally flexible diaphragm having an expanded portion at a periphery thereof, said expanded portion sealably disposed in said annular channel, said first annular flange, said second annular flange and said expanded portion defining an interface; an annular retaining member having a first inwardly protruding portion and a spaced apart second inwardly protruding portion defining a clamp channel therebetween, said first inwardly protruding portion in engagement with said shoulder of said first annular flange and said second inwardly protruding portion in engagement with said shoulder of said second annular flange, said clamp channel generally abutting said interface; and means for securing a first end of said annular retaining member to a second end of said annular retaining member around said interface so as to inhibit separation of said spring housing and said adapter base.
 17. The brake actuator of claim 16, wherein said securing means comprises an outer connector at said first end of said annular retaining member and an inner connector at said second end of said annular retaining member, said outer connector having one or more bendable tabs configured to engage a center section of said inner connector.
 18. The brake actuator of claim 17, wherein said securing means further comprises one or more retaining tabs on said inner connector, said retaining tabs configured to prevent separation of said first end and said second end of said annular retaining member.
 19. The brake actuator of claim 16, wherein said securing means comprises an outer connector at said first end of said annular retaining member and an inner connector at said second end of said annular retaining member, said outer connector having one or more apertures.
 20. The brake actuator of claim 19, wherein at least one of said one or more apertures overlays a weld receiving area on said inner connector, said outer connector and said inner connector interconnected by a weld.
 21. The brake actuator of claim 20, wherein said inner connector comprises a tab extension member at said second end of said annular retaining member, said weld receiving area on said tab extension.
 22. The brake actuator of claim 19, wherein at least one of said one or more apertures of said outer connector overlays an aperture in said inner connector, said apertures of said outer connector and said aperture of said inner connector sized and configured to receive a connecting element therein, said connecting element configured to securedly connect said first end and said second end of said annular retaining member.
 23. The brake actuator of claim 22, wherein said securing means further comprises a nut at said inner connector.
 24. The brake actuator of claim 16, wherein said annular retaining member comprises two or more clamp sections disposed about said interface to form a generally continuous curvilinear member, each of said clamp sections having a first end securedly joined to a second end of an adjacent clamp section.
 25. A method of sealably securing a spring housing to an adapter base for a tamper resistant brake actuator, said method comprising the steps of: a. providing said spring housing with a first annular flange and said adapter base with a second annular flange; b. providing a flexible diaphragm having a periphery comprising an expanded portion; c. placing the periphery of said flexible diaphragm on said second annular flange, said expanded portion disposed circumferentially about said annular flange; d. placing said spring housing over said flexible diaphragm with said first annular flange in substantial alignment with said second annular flange and said expanded portion of said flexible diaphragm; e. applying sufficient force to said spring housing and/or said adapter base to push said first annular flange over said expanded portion of said flexible diaphragm, said first annular flange and said second annular flange defining an annular channel, said expanded portion sealably disposed in said annular channel, said expanded portion forming a radial seal in said annular channel; f. installing an annular retaining member about an interface of said first annular flange, said second annular flange and said expanded portion of said flexible diaphragm, said annular retaining member having a first end and a second end; and g. securing said first end of said annular retaining member to said second end of said annular retaining member so as to inhibit unauthorized disassembly of said brake actuator.
 26. The method of claim 25, wherein said first annular flange has an outwardly extending shoulder and a downwardly extending collar and said second annular flange has an upwardly extending collar and an outwardly extending shoulder extending outwardly from the base of said collar, said shoulder and said collar of said first annular flange and said collar and said shoulder of said second annular flange forming said annular channel.
 27. The method of claim 25, wherein said first end of said annular retaining member comprises an outer connector and said second end of said annular retaining member comprises an inner connector.
 28. The method of claim 27, wherein said securing step comprises crimping one or more inwardly bendable tabs on said outer connector over a center section of said inner connector.
 29. The method of claim 28, wherein said annular retaining member further comprises one or more retaining tabs on said inner connector, said one or more retaining tabs configured to prevent separation of said first end and said second end of said annular retaining member.
 30. The method of claim 27, wherein said outer connector comprises one or more apertures, said one or more apertures overlying a weld receiving area on said inner connector, said outer connector and said inner connector joined with a weld in said aperture.
 31. The method of claim 30, wherein said inner connector comprises a tab extension, said weld receiving area on said tab extension.
 32. The method of claim 27, wherein said outer connector comprises one or more apertures overlying at least one aperture in said inner connector, said aperture in said outer connector and said aperture in said inner connector configured to receive a connecting element therein. 